1. Field of the Invention
The present invention relates generally to externally-applied wound dressings and wound closure methods.
2. Description of the Related Art
Wound-dressing and wound-healing include what is known as “moist wound healing.” Three major components that constitute the external and physical environment of the healing wound should, in an ideal wound-healing environment, be controlled. First, wound healing is inversely related to bacterial growth. Second, it has been shown that, holding other variables constant, there is a clear linear relationship between the moisture level at the wound-site and the rate of epithelial advancement. The final important characteristic is the surface contact property of the wound dressing. The surface contact property can help to control the other two major factors. The contact layer must be made of a suitable material that promotes endurance of the dressing as well as comfort to the patient.
Thin pieces of foam have been used in moist-wound healing applications. The external face of the thin foam was more open allowing for enough moisture retention initially, but then allowing drying to occur with the dressing still in place. The internal face (or tissue-contact face) had a compressed or less-open pore configuration. Because this foam did not adhere to the wound, it could be moved or removed without disrupting the epithelium. However, this practice was often limited to small incisions since the thin foam is incapable of managing a large amount of exudate from a large, fresh wound, and if exudate accumulates under the foam piece the foam will lose surface contact, which allows bacteria to build up. By preventing granulation ingrowth, the compressed surface allows epithelial migration to advance beneath the foam. However, this type of surface had even more problems staying in intimate contact with the surface, especially in the face of exudate.
In general, epithelium advances or migrates best if moisture is maximized and then matures best if moisture is minimized. Although the idea of moist wound healing is not new, the perfection and maximization of the use of this healing process is far from perfected.
Another important aspect of wound healing relates to the respective roles of the vascular and lymphatic circulatory systems, both of which are involved in wound healing, but perform different functions. An injury to tissue involves both vascular and lymphatic circulation. The vascular system clots due to the serum and platelets, which control bleeding. Lymph fluid, however, lacks comparable coagulating properties. Moreover, the smaller-channeled peripheral lymphatic system lacks the muscled walls of the vascular circulatory system or the more proximal large-channel lymphatics. Stemming the outpouring of lymph fluid from these smaller channels involves compressing the lymphatic circulatory system through surrounding tissue swelling from an accumulation of edema and interstitial fluid. Unlike the quick response of coagulating blood, lymphatic circulatory system closure tends to be slower and can take days.
Based on the involvement of the vascular and lymphatic circulatory systems in wound healing, influencing the performance of these circulatory systems can significantly improve wound healing. Wound closure can be achieved more quickly and infection risks can be reduced by controlling the factors affecting vascular and lymphatic circulation. For example, increased perfusion of blood flow in the wound site generally promotes healing and reepithelialization. Individual cells are also responsive to mechano-inductive forces, such as compression and tension. Properly applied and sequenced, compression and tension can promote healing.
The present invention addresses these wound healing factors by controlling and directing compression, tension and other physiological variables associated with the tissues and the fluids associated with the wound site and otherwise involved in the wound healing process.